S: Use weight range: 12 catties or less (general recommendation) waist circumference less than 30cm. M: Use weight range: below 14 catties (general recommendation) waist circumference less than 40cm. L: Use weight range: below 16 catties (regular recommendation) waist circumference less than 60cm. 4 ways to set: 1. No entry but no exit (completely closed); 2. (Exit but no entry (completely open); 3. Only entry but no exit; 4. Only exit but no entry.< br>Installation method: 1: First use a piece of paper to draw the size of the door cover (there may be a few millimeters error); 2: Make a good drawing on the door and draw a good print with a pencil; 3: After drawing Use a drill to drill a hole in the four corners of the door, and then start to dig the hole directly if there is a chainsaw; 4: If it is a glass door, use a glass scribing tool to gently cut it, and fix it with glass glue; 5: The hole has been cleaned up, now first get a layer of wood leather to wrap around the hole, for the sake of beauty; 6: install the cat door, there are accessory screws, use a screwdriver to tighten; 7: the screw port is also equipped with screws Lid, press on, ok, finished.